Positioning a product against a competitor is much like positioning a political candidate against a competitor.
Barack Obama, though he still trails Hillary Clinton in most polls, is the current "darling" of the Democratic field of presidential candidates. Clinton's "positives" may be high, but so are her "negatives" (most people have formed an opinion about her one way or the other).
According to polls, Obama's "positives" far outweigh his "negatives". His biggest strength is that he is a fresh face.
A good marketer - and a good campaign strategist - knows that the best way to defeat a competitor is to find the weakness within his strength and attack at that point.
If being a fresh face is Obama's biggest strength, then it's also a weakness. Maybe he doesn't have the foreign policy experience needed to confront the threat of terrorism. Maybe he doesn't have the executive experience to lead a nation. Whoever runs against Obama should find a focused issue, or something specific in his past, that exemplifies Obama's lack of experience and the liabilities of it.
Obama, on the other hand, should embrace his weakness. He could, for example, acknowledge his inexperience with foreign policy but find a way of spinning it as a strength. Perhaps the world has become so disenchanted with the United States and its leaders that a fresh face with a new approach is just what the United States needs. Whatever; Obama can't deny his lack of experience, so he should find specific ways of showing how it is a strength.
It will be interesting to see which Democratic candidate's campaign strategists understand and apply the principles of product positioning.